Add a convenient leaf handler

This adds a convenient handler class for elements that consist only
of attributes.

Affects: #2

com.io7m.blackthorne.api/pom.xml

@@ -8,7 +8,7 @@
   <parent>
     <artifactId>com.io7m.blackthorne</artifactId>
     <groupId>com.io7m.blackthorne</groupId>
-    <version>1.0.1-SNAPSHOT</version>
+    <version>1.1.0-SNAPSHOT</version>
   </parent>
 
   <artifactId>com.io7m.blackthorne.api</artifactId>

com.io7m.blackthorne.api/src/main/java/com/io7m/blackthorne/api/BTLeafElementHandler.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright © 2019 Mark Raynsford <code@io7m.com> http://io7m.com
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
+ * IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+
+package com.io7m.blackthorne.api;
+
+import org.xml.sax.Attributes;
+import org.xml.sax.SAXException;
+
+import java.util.Objects;
+
+/**
+ * A convenient handler dealing with elements that do not have children.
+ *
+ * @param <S> The type of returned values
+ */
+
+public final class BTLeafElementHandler<S>
+  implements BTElementHandlerType<Object, S>
+{
+  private final BTQualifiedName name;
+  private final BTLeafElementHandlerType<S> handler;
+  private S result;
+
+  /**
+   * Construct a handler.
+   *
+   * @param inName    The name of elements handled by this handler
+   * @param inHandler The element handler
+   */
+
+  public BTLeafElementHandler(
+    final BTQualifiedName inName,
+    final BTLeafElementHandlerType<S> inHandler)
+  {
+    this.name =
+      Objects.requireNonNull(inName, "name");
+    this.handler =
+      Objects.requireNonNull(inHandler, "handler");
+  }
+
+  @Override
+  public String name()
+  {
+    return this.name.localName();
+  }
+
+  @Override
+  public void onElementStart(
+    final BTElementParsingContextType context,
+    final Attributes attributes)
+    throws SAXException
+  {
+    try {
+      this.result = this.handler.onElement(context, attributes);
+    } catch (final Exception e) {
+      throw context.parseException(e);
+    }
+  }
+
+  @Override
+  public S onElementFinished(
+    final BTElementParsingContextType context)
+  {
+    return this.result;
+  }
+}

com.io7m.blackthorne.api/src/main/java/com/io7m/blackthorne/api/BTLeafElementHandlerType.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright © 2020 Mark Raynsford <code@io7m.com> http://io7m.com
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
+ * IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+package com.io7m.blackthorne.api;
+
+import org.xml.sax.Attributes;
+
+/**
+ * An element handler that takes the attributes of a single element and
+ * produces an output value.
+ *
+ * @param <S> The type of returned values
+ */
+
+public interface BTLeafElementHandlerType<S>
+{
+  /**
+   * Process the attributes of an element.
+   *
+   * @param context    The parse context
+   * @param attributes The element attributes
+   *
+   * @return A value of {@code S}
+   *
+   * @throws Exception On errors
+   */
+
+  S onElement(
+    BTElementParsingContextType context,
+    Attributes attributes)
+    throws Exception;
+}

com.io7m.blackthorne.api/src/main/java/com/io7m/blackthorne/api/package-info.java

@@ -19,7 +19,7 @@
  */
 
 @Export
-@Version("1.0.0")
+@Version("1.1.0")
 package com.io7m.blackthorne.api;
 
 import org.osgi.annotation.bundle.Export;

com.io7m.blackthorne.jxe/pom.xml

@@ -8,7 +8,7 @@
   <parent>
     <artifactId>com.io7m.blackthorne</artifactId>
     <groupId>com.io7m.blackthorne</groupId>
-    <version>1.0.1-SNAPSHOT</version>
+    <version>1.1.0-SNAPSHOT</version>
   </parent>
 
   <artifactId>com.io7m.blackthorne.jxe</artifactId>

com.io7m.blackthorne.tests/pom.xml

@@ -8,7 +8,7 @@
   <parent>
     <artifactId>com.io7m.blackthorne</artifactId>
     <groupId>com.io7m.blackthorne</groupId>
-    <version>1.0.1-SNAPSHOT</version>
+    <version>1.1.0-SNAPSHOT</version>
   </parent>
 
   <artifactId>com.io7m.blackthorne.tests</artifactId>

com.io7m.blackthorne.tests/src/test/java/com/io7m/blackthorne/tests/BlackthorneTest.java

@@ -22,6 +22,7 @@
 import com.io7m.blackthorne.api.BTElementParsingContextType;
 import com.io7m.blackthorne.api.BTException;
 import com.io7m.blackthorne.api.BTIgnoreUnrecognizedElements;
+import com.io7m.blackthorne.api.BTLeafElementHandler;
 import com.io7m.blackthorne.api.BTParseError;
 import com.io7m.blackthorne.api.BTQualifiedName;
 import com.io7m.blackthorne.api.Blackthorne;
@@ -1246,4 +1247,35 @@ public void testConvenience1()
     Assertions.assertEquals(SAXParseException.class, ex.getCause().getClass());
     Assertions.assertEquals(2, ex.errors().size());
   }
+
+  /**
+   * Leaf element handlers work.
+   *
+   * @throws Exception On errors
+   */
+
+  @Test
+  public void testLeafIntegerAttr0()
+    throws Exception
+  {
+    final var intAttr =
+      new BTLeafElementHandler<>(
+        BTQualifiedName.of("urn:tests", "intA"),
+        BlackthorneTest::parseIntAttribute
+      );
+
+    final var handler =
+      BTContentHandler.<Number>builder()
+        .addHandler("urn:tests", "intA", context -> intAttr)
+        .build(URI.create("urn:text"), this::logError);
+
+    final var reader = createReader();
+    reader.setContentHandler(handler);
+    reader.setErrorHandler(handler);
+    reader.parse(resource("intA.xml"));
+
+    Assertions.assertFalse(handler.failed());
+    Assertions.assertEquals(0, this.errors.size());
+    Assertions.assertEquals(BigInteger.valueOf(23L), handler.result().get());
+  }
 }

pom.xml

@@ -13,7 +13,7 @@
 
   <groupId>com.io7m.blackthorne</groupId>
   <artifactId>com.io7m.blackthorne</artifactId>
-  <version>1.0.1-SNAPSHOT</version>
+  <version>1.1.0-SNAPSHOT</version>
   <packaging>pom</packaging>
 
   <name>com.io7m.blackthorne</name>
@@ -33,7 +33,7 @@
     <com.io7m.immutables.version>2.7.5</com.io7m.immutables.version>
     <com.io7m.junit.version>5.7.0</com.io7m.junit.version>
     <com.io7m.jxe.version>1.0.0</com.io7m.jxe.version>
-    <io7m.api.previousVersion>0.0.1-SNAPSHOT</io7m.api.previousVersion>
+    <io7m.api.previousVersion>1.0.0</io7m.api.previousVersion>
   </properties>
 
   <licenses>